More must be done to help parents and teachers spot signs of mental illness in children or thousands of youngsters could be at risk of alcohol and drug abuse, self-harm and even suicide, UK experts have warned.

A group of child health specialists have cautioned that many children are at risk of “slipping through the net” if awareness is not improved among adults.

The comments come as a new survey found that more than a third of adults are unsure about the signs of mental illness in a child.

And over half fear approaching the subject in case they are mistaken.

The poll of 2100 British adults found 38 per cent did not know the signs and symptoms of mental illness in youngsters and 51 per cent would be worried about raising the issue for fear of being wrong.

Meanwhile more than a third of men polled believe many children diagnosed with a mental health condition were just “badly behaved”.

The news comes as a new website has been launched to try to teach adults about mental illness in youngsters.

The Department of Health-funded site, www.minded.org.uk, aims to address a lack of understanding around mental illness in youngsters.

A number of leading health bodies have contributed to the site including the Royal College of Paediatrics and Child Health, the Royal College of Psychiatrists and charity YoungMinds.

A spokeswoman for the website said: “Without increased education or awareness to help adults identify and understand children and young people with mental health issues, thousands are at increased risk of alcohol and drug misuse, self-harm, neglect and in extreme cases, suicide.”

The Royal College of Psychiatrists said it would be an “invaluable” tool for people who work with children and young people.

It warned that there has been a large increase in mental illness among youngsters over the last 25 years – with one in 10 suffering from a diagnosable mental disorder.

Dr Raphael Kelvin, child psychiatrist and clinical lead for the MindEd program, said: “Half of all diagnosable mental health conditions start before the age of 14 and 75 per cent by the age of 21, so identifying children at the earliest opportunity is crucial in setting them on the best path in life.

“It’s clear from these results that there’s still stigma attached to mental health.

“It’s also clear that many adults are not confident in being able to spot the signs of ill mental health in children. So it’s vital that people know what to look out for so they can address the issue before it worsens and that’s where MindEd can help.”

Care and Support Minister Norman Lamb said spotting the signs of mental health problems early in children and young people was essential to prevent problems from escalating and continuing into adulthood.

“That’s why we have invested STG3 million ($A5.45 million) in MindEd – so that people working with children, from teachers to dinner ladies and sports coaches to Scouts leaders, can recognise when a child needs help and make sure they get it.”